If you need an index value associated with a list, use Enum.with_index/2
# I have a list
list = ["a", "b", "c"]
# with_index returns the enumerable with each element
# wrapped in a tuple alongside its index.
iex > Enum.with_index(list)
# [{"a", 0}, {"b", 1}, {"c", 2}]
# Provide an offset and you start at 1 instead of 0
iex > Enum.with_index(list, 1)
# [{"a", 1}, {"b", 2}, {"c", 3}]Keep in mind you will get a list of tuples with the element and the index value inside of it (as shown above).
When you are looping over a list you can use comprehension to get both the item and index.
for {item, index} <- Enum.with_index(list) do
"#{item} is at index #{index}"
end
# ["a is at index 0", "b is at index 1", "c is at index 2"]
# Pass in the offset and start at 1 instead of 0
for {item, index} <- Enum.with_index(list, 1) do
"#{item} is at index #{index}"
end
# ["a is at index 1", "b is at index 2", "c is at index 3"]